title: Sediment trapping by dams creates methane emission hot spots.
abstract: Inland waters transport and transform substantial amounts of carbon and account for ∼18% of global methane emissions. Large reservoirs with higher areal methane release rates than natural waters contribute significantly to freshwater emissions. However, there are millions of small dams worldwide that receive and trap high loads of organic carbon and can therefore potentially emit significant amounts of methane to the atmosphere. We evaluated the effect of damming on methane emissions in a central European impounded river. Direct comparison of riverine and reservoir reaches, where sedimentation in the latter is increased due to trapping by dams, revealed that the reservoir reaches are the major source of methane emissions (∼0.23 mmol CH4 m(-2) d(-1) vs ∼19.7 mmol CH4 m(-2) d(-1), respectively) and that areal emission rates far exceed previous estimates for temperate reservoirs or rivers. We show that sediment accumulation correlates with methane production and subsequent ebullitive release rates and may therefore be an excellent proxy for estimating methane emissions from small reservoirs. Our results suggest that sedimentation-driven methane emissions from dammed river hot spot sites can potentially increase global freshwater emissions by up to 7%.
authors.affiliation: Institute for Environmental Sciences, University of Koblenz-Landau , 76829 Landau, Germany. maeck@uni-landau.de
authors.forename: Andreas
authors.initials: A
authors.lastname: Maeck
authors.forename: Tonya
authors.initials: T
authors.lastname: Delsontro
authors.forename: Daniel F
authors.initials: DF
authors.lastname: McGinnis
authors.forename: Helmut
authors.initials: H
authors.lastname: Fischer
authors.forename: Sabine
authors.initials: S
authors.lastname: Flury
authors.forename: Mark
authors.initials: M
authors.lastname: Schmidt
authors.forename: Peer
authors.initials: P
authors.lastname: Fietzek
authors.forename: Andreas
authors.initials: A
authors.lastname: Lorke
mesh_terms: D005060:Europe; D005618:Fresh Water; D019015:Geologic Sediments; D008697:Methane / Q000032:analysis*; D045483:Rivers; D012621:Seasons; D014874:Water Pollutants, Chemical / Q000032:analysis*
chemical_list: D014874:Water Pollutants, Chemical; D008697:Methane